The Problem with Commercial Fish Farming

I came across a rather disturbing article a couple of weeks ago that stated if current trends continue, then all fish in the world’s oceans will be gone by 2050. Whether or not that is an accurate assessment, the fact remains that over-fishing and pollution are posing an ever-increasing threat to commercial fish populations. In the past couple decades, commercial fish farming has become a very popular way to help circumvent these omens of disasters. However, fish farming poses a paradox in itself, and currently is not accomplishing its goal of reducing our dependence on the ocean.

Humans love fish, and many areas depend on commercial fishing for economic reasons. Fish is generally a healthier source of protein than red meat, containing among other nutrients high levels of omega-3 fatty acids. Thus, it would make sense to focus on farming fish more than livestock. Fish farming has a number of benefits, including an ability to closely monitor fish hatches and maximize populations. Furthermore, risks of pollutants in commercially-raised fish are diminished. In the ocean, certain organisms called mysids are food for large fish that we eat. However, mysids can absorb many pollutant toxins before dying, and those toxins are transferred to fish we eat. Commercial fish farming can help reduce this risk. Although the practice of fish farming seems like a good idea and one that can help the environment, the reality of fish farming is not quite as simple.

The majority of the commonly consumed fish in the world market are carnivorous, meaning that they consume other fish, crustaceans, or underwater fauna in order to survive. Furthermore, a majority of our commonly eaten fish come from the ocean. Oceanic ecosystems are much different than terrestrial or freshwater ones. The biggest difference is in the food chain. There are many more steps in the food chain in the oceans than there are on land-based environments. Since the ocean is very deep and sunlight cannot reach the bottom, ocean plants are much less bountiful than terrestrial plants, except in shallow seas or reef areas. This is another story in freshwater ponds, lakes, and rivers, where adequate sunlight can reach the soil on the bottom of the body of water and allow plant growth. Thus, the basis for ocean food chains really begins with phytoplankton rather than with plants. Phytoplankton is comprised of tiny organisms that are consumed by everything from small fish to gigantic baleen whales. The fish we commonly eat consume smaller fish that feed on phytoplankton.

What does this mean for fish farming? Well, in order to raise salmon or cod for example, you need to provide them with either processed fish food or living fish to feed on. This means that either smaller fish/plankton must be farmed as well to provide food for larger fish, or they must be obtained from the ocean. Getting plankton and small fish from the world’s oceans only helps expedite the process of commercial over-fishing because it reduces the amount of base-level food chain members in the ecosystem. Instead of reducing dependence on ocean fishing, the majority of commercial fish farming actually increases that dependence.

What can be done? A few things, actually. Technology has progressed to the point where varieties of phytoplankton and small crustaceans can be farmed effectively and processed as food for fish. This means that filter-feeding fish such as carp and tilapia can be better supported. Filter feeders are less expensive to farm and less detrimental to ocean ecosystems because they are lower in the food chain and feed on phytoplankton. Furthermore, it would be in the best interests of commercial fish farms to switch the emphasis of from carnivorous to herbivorous fish such as parrotfish or surgeonfish. Farming herbivorous fish and filter feeders improves the net gain of protein from this kind of farming. Salmon, though extremely popular and good to eat, is no better raised in a fish farm than fished from the oceans and rivers.

Fish farming is an industry that has enormous potential, and may help to alleviate some of the stress that humans have placed on the oceans. However, changes in practice will be necessary before any kind of progress in ecological impact is achieved.